Full explanation
Optimal windows across Ukraine: winter wheat — South 15.09–05.10, Forest-Steppe 05.09–25.09, Polissia 01.09–15.09; winter rapeseed — West 15.08–25.08, Center 20.08–30.08, South 25.08–05.09 (needs to reach 8–10 leaf rosette before frost); spring barley — at soil temperature +4–5°C at 10 cm depth (late March to early April most of Ukraine); corn — at soil +10–12°C (late April to early May); sunflower — +8–10°C (1st–3rd decade April); soybean — +12–14°C (3rd decade April to 1st decade May); sugar beet — +6–8°C (2nd–3rd decade April). Delays of 5–10 days past optimum usually cost 5–15% yield due to: insufficient autumn tillering (winter crops), entering summer drought at critical stages (spring crops). Earlier than optimum risks: seedling frost, intense autumn disease on winter crops (Septoria, Cercospora), weak winter hardiness from overgrowth.